3 files changed, 35 insertions, 17 deletions
diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index e09b0685d41..221dcf23f7f 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -27,6 +27,7 @@ use layers::rendergl;
 use layers::scene::Scene;
 use msg::compositor_msg::{Epoch, LayerId};
 use msg::compositor_msg::{ReadyState, PaintState, ScrollPolicy};
+use msg::constellation_msg::AnimationState;
 use msg::constellation_msg::Msg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, NavigationDirection};
 use msg::constellation_msg::{Key, KeyModifiers, KeyState, LoadData};
@@ -166,8 +167,11 @@ struct PipelineDetails {
     /// The status of this pipeline's PaintTask.
     paint_state: PaintState,
 
-    /// Whether animations are running.
+    /// Whether animations are running
     animations_running: bool,
+
+    /// Whether there are animation callbacks
+    animation_callbacks_running: bool,
 }
 
 impl PipelineDetails {
@@ -177,6 +181,7 @@ impl PipelineDetails {
             ready_state: ReadyState::Blank,
             paint_state: PaintState::Painting,
             animations_running: false,
+            animation_callbacks_running: false,
         }
     }
 }
@@ -278,9 +283,9 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                 self.change_paint_state(pipeline_id, paint_state);
             }
 
-            (Msg::ChangeRunningAnimationsState(pipeline_id, running_animations),
+            (Msg::ChangeRunningAnimationsState(pipeline_id, animation_state),
              ShutdownState::NotShuttingDown) => {
-                self.change_running_animations_state(pipeline_id, running_animations);
+                self.change_running_animations_state(pipeline_id, animation_state);
             }
 
             (Msg::ChangePageTitle(pipeline_id, title), ShutdownState::NotShuttingDown) => {
@@ -422,11 +427,22 @@ impl<Window: WindowMethods> IOCompositor<Window> {
     /// recomposite if necessary.
     fn change_running_animations_state(&mut self,
                                        pipeline_id: PipelineId,
-                                       animations_running: bool) {
-        self.get_or_create_pipeline_details(pipeline_id).animations_running = animations_running;
-
-        if animations_running {
-            self.composite_if_necessary(CompositingReason::Animation);
+                                       animation_state: AnimationState) {
+        match animation_state {
+            AnimationState::AnimationsPresent => {
+                self.get_or_create_pipeline_details(pipeline_id).animations_running = true;
+                self.composite_if_necessary(CompositingReason::Animation);
+            }
+            AnimationState::AnimationCallbacksPresent => {
+                self.get_or_create_pipeline_details(pipeline_id).animation_callbacks_running = true;
+                self.composite_if_necessary(CompositingReason::Animation);
+            }
+            AnimationState::NoAnimationsPresent => {
+                self.get_or_create_pipeline_details(pipeline_id).animations_running = false;
+            }
+            AnimationState::NoAnimationCallbacksPresent => {
+                self.get_or_create_pipeline_details(pipeline_id).animation_callbacks_running = false;
+            }
         }
     }
 
@@ -921,10 +937,11 @@ impl<Window: WindowMethods> IOCompositor<Window> {
     /// If there are any animations running, dispatches appropriate messages to the constellation.
     fn process_animations(&mut self) {
         for (pipeline_id, pipeline_details) in self.pipeline_details.iter() {
-            if !pipeline_details.animations_running {
-                continue
+            if pipeline_details.animations_running ||
+               pipeline_details.animation_callbacks_running {
+
+                self.constellation_chan.0.send(ConstellationMsg::TickAnimation(*pipeline_id)).unwrap();
             }
-            self.constellation_chan.0.send(ConstellationMsg::TickAnimation(*pipeline_id)).unwrap();
         }
     }
 
diff --git a/components/compositing/compositor_task.rs b/components/compositing/compositor_task.rs
index acafbbc8f9b..0f2b1249703 100644
--- a/components/compositing/compositor_task.rs
+++ b/components/compositing/compositor_task.rs
@@ -19,7 +19,7 @@ use layers::platform::surface::{NativeCompositingGraphicsContext, NativeGraphics
 use layers::layers::LayerBufferSet;
 use msg::compositor_msg::{Epoch, LayerId, LayerMetadata, ReadyState};
 use msg::compositor_msg::{PaintListener, PaintState, ScriptListener, ScrollPolicy};
-use msg::constellation_msg::{ConstellationChan, PipelineId};
+use msg::constellation_msg::{AnimationState, ConstellationChan, PipelineId};
 use msg::constellation_msg::{Key, KeyState, KeyModifiers};
 use profile_traits::mem;
 use profile_traits::time;
@@ -202,7 +202,7 @@ pub enum Msg {
     /// Alerts the compositor that the current page has changed its URL.
     ChangePageUrl(PipelineId, Url),
     /// Alerts the compositor that the given pipeline has changed whether it is running animations.
-    ChangeRunningAnimationsState(PipelineId, bool),
+    ChangeRunningAnimationsState(PipelineId, AnimationState),
     /// Alerts the compositor that a `PaintMsg` has been discarded.
     PaintMsgDiscarded,
     /// Replaces the current frame tree, typically called during main frame navigation.
diff --git a/components/compositing/constellation.rs b/components/compositing/constellation.rs
index a9271bc0cfd..5b69a678117 100644
--- a/components/compositing/constellation.rs
+++ b/components/compositing/constellation.rs
@@ -14,6 +14,7 @@ use gfx::font_cache_task::FontCacheTask;
 use layout_traits::{LayoutControlMsg, LayoutTaskFactory};
 use libc;
 use msg::compositor_msg::LayerId;
+use msg::constellation_msg::AnimationState;
 use msg::constellation_msg::Msg as ConstellationMsg;
 use msg::constellation_msg::{FrameId, PipelineExitType, PipelineId};
 use msg::constellation_msg::{IFrameSandboxState, MozBrowserEvent, NavigationDirection};
@@ -344,8 +345,8 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
                                                             sandbox);
             }
             ConstellationMsg::SetCursor(cursor) => self.handle_set_cursor_msg(cursor),
-            ConstellationMsg::ChangeRunningAnimationsState(pipeline_id, animations_running) => {
-                self.handle_change_running_animations_state(pipeline_id, animations_running)
+            ConstellationMsg::ChangeRunningAnimationsState(pipeline_id, animation_state) => {
+                self.handle_change_running_animations_state(pipeline_id, animation_state)
             }
             ConstellationMsg::TickAnimation(pipeline_id) => {
                 self.handle_tick_animation(pipeline_id)
@@ -560,9 +561,9 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
 
     fn handle_change_running_animations_state(&mut self,
                                               pipeline_id: PipelineId,
-                                              animations_running: bool) {
+                                              animation_state: AnimationState) {
         self.compositor_proxy.send(CompositorMsg::ChangeRunningAnimationsState(pipeline_id,
-                                                                               animations_running))
+                                                                               animation_state))
     }
 
     fn handle_tick_animation(&mut self, pipeline_id: PipelineId) {